[Oberon] Oberon-7 - Circle Segments

[Jörg]

cos 30° = sqrt(3)/2. Here the rational numbers approximating cos 30° better and better:
13 / 15           error =   0.06%
58 / 67           error =   0.04%
71 / 82           error =   0.02%
84 / 97           error = 460 x10-7
181 / 209      error =   33 x10-7
808 / 933      error =   18 x10-7
989 / 1142    error =     9 x10-7
1170 / 1351  error =     2 x10-7

br
Jörg

Am 20.02.19, 09:40 schrieb "Oberon im Auftrag von Tomas Kral" <oberon-bounces at lists.inf.ethz.ch im Auftrag von thomas.kral at email.cz>:

    On Tue, 19 Feb 2019 20:06:34 +0100
    Jörg <joerg.straube at iaeth.ch> wrote:
    
    >   s:= r DIV 2; c := r * 181 DIV 209;
    >   x[0] := 0; y[0] := r;
    >   x[1] := s; y[1] := c;
    >   x[2] := c; y[2] := s;
    
    Aha, 
    
    we start with one quadrant as the rest is the symetry.
    Quadrant = 90 / 3 = 30 deg. sin(30) = 0.5 first triangle, the
    other is cos(30). 
    
    181 / 209 big enough triangle with angle proximing to 30 deg.
    
    -- 
    Tomas Kral <thomas.kral at email.cz>
    --
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